Reservations from Kolding (DK) to Vaduz (LI)

Most likely, there's no mistake. Railways use yield management for long distance trains, so trains that are busier will be more expensive than quieter trains. In addition, DSB could use another system than DB (although I thought DSB were also booking via the DB system but I may be wrong). In any case, it's useful to compare prices on different websites and for different connections.

Yes there are, e.g. from Hamburg to Zurich would be interesting for you.

If the train has the name Nightjet. But with nightjet it is not possible to book as one ticket from Denmark to Switzerland due to different booking pages. You get 2-3 tickets instead.

With Interrail you only need a reservation for the Nightjet (starting from 14€ for seats to Austria, seats to Switzerland run as normal Intercity train of DB, without reservation. Couchette end sleeper need a reservation in any case).

Do you have interrail passes? What are the dates you will be travelling?

Without exact dates and times it's difficult to advise.

The station is called Schaan-Vaduz normally. 

Note Vaduz does not have a train station, but Schaan (4 km away) does. However, Schaan is only served by local trains between Feldkirch (Austria) and Buchs (Switzerland) from Monday to Friday only. No service in weekends.

The DB travel planner is probably giving you an option including a bus from either Feldkirch, Buchs or Sargans. These buses do actually go to Vaduz and are far more frequent and not much slower than the train to Schaan, but those are not covered Interrail - you can however buy a separate ticket for them - I think I did so on board of the bus. I'd recommend you'd search for a journey to either Feldkirch, Buchs or Sargans, and check the bus timetables from those towns on liemobil.li.

Hope this helps!

A quick search gace me tickets for about 180 to 250 EUR (one way) for the four of you on a random monday next month, from Kolding to Sargans. Interrail wil cost at least as much per person, except for your child. 

1. I don't think so. A pass is only interesting if you do more trips (or if you're a bit last minute, sometimes it's the cheaper option). Check ordinary prices and your travel date and compare. Liechtenstein is not big, so if you plan daytrips to Switzerland or Austria you might get more value for money with interrail. 

2. Yes (see above)

3. Deutsche Bahn or SBB for your connection.

4. The map is very bad, and only depicts very few, very cliché destinations. Interrail validity should be seen per company. Check:  https://www.interrail.eu/en/plan-your-trip/tips-and-tricks/trains-europe/railway-companies to know which companies are included. De facto 95% of all European trains ( of which some require seat reservations, but not on the route you'll be taking. Seat reservations are optional on IC and ICE. The rest of your trains doesn't even require reservations ) 

@viking if you state the dates and times you want to leave for Liechtenstein, we can tell you what option (ordinary tickets or interrail) is the most value for money. Prices can differ a lot on long distance trains.

To answer your next questions:

1. Yes, look at the companies, not the maps. More than 40000 stations can be reached with interrail. It's a real golden hyperflexible ticket! 

2. For example, but Liechtenstein is smaller than the average municipality, it's a micro state. So ordinary tickets will be cheaper anyhow. You won't pay 100 EUR to get from Vaduz to Nendeln 1,5 km away, more like 2 EUR 😅. A pass day is worth about 60 EUR for a 4 day flexible pass.

A 7day pass will be overkill for a week. But if you'lld combine  going to Liechtensteun and want to go for a day trip from Liechtenstein to Zürich, Innsbruck, Ulm or Sankt Moritz e.g.,a 4 day Interrail global pass will be good value for money! 2 days needed to get to/from Kolding to Liechtenstein and two days where you can do daytrips. But always compare to ordinary prices. It's not necessarily the cheapest option. But if you just spend a week in Liechtenstein without any daytrips, just stick with ordinary tickets :)

3. A lot of trains you cannot even reserve. If its wise to reserve on the ones where it's optional... Hmm, it really depends when you'll be travelling. So again, if you tell us when you want to make your trip to Liechtenstein, we can tell if you'lld better get seat reservations for Deutsche Bahn or not.

Fridays and Sunday evenings are usually busy on long distance trains. Same counts for long weekends and beginning and endings of holiday periods (like Christmas, Easter, or weekends during summer holidays). But if you travel off-peak on a random tuesday in the middle of February, you'll have all the place you want without reservations. 

For the Bernina Express you can even ride with the same train as there always are reservation free coaches (right behind the engine if I remember correctly).

I get connections with the night jet on DB. But that is with the night train leaving Köln just before midnight, which not might be a good idea when you have a small child. 

I suggest you check trains between Kolding and Hamburg. Then there is a night train between Hamburg and Zürich. In Zürich you take another train to Sargans.

It does. It should also be possible to get Hamburg - Zürich for that price, unless the coaches to Zürich are already full (half the train only goes to Basel). I do see it on tickets.oebb.at: 3 adults and 1 child Hamburg - Zürich for €199.

[1]

Regarding just the booking of a sleeper or couchette compartment for the nighttrain (as shown in your own post), there’s no need to compare. DB is booking the night train with ÖBB booking system, so there’s no difference. 

Private means private. I don’t think this is misleading. It’s a private compartment (= Abteil) just for you. No other people are allowed to join.

There are 6 berths. But it’s possible to keep two of them folded away so you’ll also get a configuration with just 4 beds in the same compartment - you’ll see how it looks like following the link [3].

[2]

It’s not the same. A Privatabteil is private (no other person may join), Liegeplatz im Abteil mit 6 Liegen means that there are two (if you pay for your child) or three other people (if you don’t pay for your child) that may get booked in your compartment - it’s not private. So the cheaper offer is the better one. But for the date shown in your post there’s just one compartement left for 199 € - if someone books it, it’s gone - it’s just a special offer. But remember again: if you’ll buy an interrail pass, it would be complete nonsense to buy any of these offers. Both offers are complete tickets (ticket and reservation) for which you won’t need an interrail pass. 

[3]

The train operators website does show it: Couchette - Nightjet

[4]

The price of the interrail pass itself is not the same (normally, there are special offers every year - but the last one did just end last week). 

There is no pass fare for a private compartment on a Nightjet.

These prices are not really special offers. They're always there but availability is limited and the chance to get them is higher when it's not so busy (like now).

Nightjet does not have a class distinction.

Sleeper compartments often have 3 berths but can also be set up for 2 persons or 1 person. You will always have a private sleeper compartment if you book 3 berths in a 3-berth compartment (T3), 2 berths in a 2-berth compartment (Double) and 1 berth in a 1-berth compartment (Single). "Double” and "Single” are often just the same compartment but with a different set-up.

That must have been temporary. Normal fares start from CHF 2 and for international lines to/from Switzerland, there's a combined fare of Liechtenstein + Ostwind fare.